# std::linear_congruential_engine

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< cpp‎ | numeric‎ | random

Defined in header `<random>` |  |
template< class UIntType, UIntType a, UIntType c, UIntType m > class linear_congruential_engine; |  | (since C++11)

`linear_congruential_engine` is a random number engine based on Linear congruential generator (LCG).

### Template parameters

UIntType | - | The result type generated by the generator. The effect is undefined if this is not one of unsigned short, unsigned int, unsigned long, or unsigned long long.
a | - | the multiplier term
c | - | the increment term
m | - | the modulus term

When m is not zero, if a >= m or c >= m is true, the program is ill-formed.

### Generator properties

The size of the states of `linear_congruential_engine` is 1, each of them consists of a single integer.

The actual modulus \(\scriptsize m_0\)m0 is defined as follows:

- If m is not zero, \(\scriptsize m_0\)m0 is m.
- If m is zero, \(\scriptsize m_0\)m0 is the value of std::numeric_limits<result_type>::max() plus 1 (which means \(\scriptsize m_0\)m0 need not be representable as `result_type`).

The transition algorithm of `linear_congruential_engine` is \(\scriptsize TA(x_i) = (a \cdot x_i + c)\mod m_0\)TA(xi) = (a·xi+c) mod m0.

The generation algorithm of `linear_congruential_engine` is \(\scriptsize GA(x_i) = (a \cdot x_i + c)\mod m_0\)GA(xi) = (a·xi+c) mod m0.

The pseudo-random number generated with the current state is also the successor state.

### Predefined specializations

The following specializations define the random number engine with two commonly used parameter sets:

Defined in header `<random>`
Type | Definition
`minstd_rand0` (C++11) | std::linear_congruential_engine<std::uint_fast32_t, `` 16807, 0, 2147483647> Discovered in 1969 by Lewis, Goodman and Miller, adopted as "Minimal standard" in 1988 by Park and Miller
`minstd_rand` (C++11) | std::linear_congruential_engine<std::uint_fast32_t, `` 48271, 0, 2147483647> Newer "Minimum standard", recommended by Park, Miller, and Stockmeyer in 1993

### Nested types

Type | Definition
`result_type` | `UIntType`

### Data members

constexpr UIntType multiplier [static] | a (public static member constant)
constexpr UIntType increment [static] | c (public static member constant)
constexpr UIntType modulus [static] | m (public static member constant)
constexpr UIntType default_seed [static] | 1u (public static member constant)

### Member functions

##### Construction and Seeding
(constructor) | constructs the engine (public member function)
seed | sets the current state of the engine (public member function)
##### Generation
operator() | advances the engine's state and returns the generated value (public member function)
discard | advances the engine's state by a specified amount (public member function)
##### Characteristics
min [static] | gets the smallest possible value in the output range (public static member function)
max [static] | gets the largest possible value in the output range (public static member function)

### Non-member functions

operator==operator!= (C++11)(C++11)(removed in C++20) | compares the internal states of two pseudo-random number engines (function)
operator<<operator>> (C++11) | performs stream input and output on pseudo-random number engine (function template)

### Example

| This section is incomplete Reason: no example

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